basically saw a bike shop on facebook selling these jekyll frames with the description saying the rear suspension is “DNM coil switchback pull type rear sus”. i tried looking it up and nothing is showing up, im really curious about it and how it performs
by dajacobinclab
3 Comments
What it is, is the same proprietary bullshit that Cannondale always puts out that you want to stay away from. Proprietary stuff like this is generally harder to find parts for and the parts are more expensive.
As far as how it works, as the rear compresses under load linkage in the top left (first photo) moves forward. During this motion the place that the black four-link is mounted to the frame and the linkage get pulled away from each other, flattening out the shape of the four-link and compressing the shock.
Yeah I can help ya with the concept. See the upper most forward link painted off-white, starting just above the first “N” in Cannondale of the front triangle? As the suspension compresses, that link moves forward. The original shocks on these frames were pull shocks that resist becoming longer. The vast majority of shocks are made as push shocks, they resist getting shorter. When the pull shock wears out and perhaps someone is not having a good time with Cannondale corporate, they become desperate and want some way of installing a push shock they can maintain. That black linkage works like a scissor lift, but backwards. As the linkage is pulled apart, the middle pivots move closer together, thus compressing the specific replacement coil push shock.
I [make bike stuff](http://www.regular.bike) and am presently engrossed in designing a linkage front suspension fork specifically because I do not like issues exactly like this one where replacing the shock guts (when the inevitably wear from use) becomes so very frustrating due to supply chain and customer service stuff.
~~Pull shocks work opposite of more standard push shocks, the linkage extended a pull shocks during suspension compression. Cannondale is the only one that’s ever really used it, they use proprietary shocks so you have very very limited replacement options and customization. And in a few years support will be dropped or limited and you’ll be sol if you need and parts, service, or replacements~~
Edit: not a pull shock